Reactive vs. Neoplastic Astrocytes

Astrocytes are star-shaped glial cells that comprise a large proportion of brain tissue.  Non-neoplastic reactive astrocytes can sometimes be difficult to differentiate from the neoplastic astrocytes of glial tumors called astrocytomas.  This GFAP stain highlights the key morphologic differences between the star-shaped and widely spread-out non-neoplastic reactive astrocytes compared to the neoplastic astrocytes in this glioblastoma, which exhibit crowding and severe variation in size and shape (i.e. pleomorphism).